Electrostatic ignition system



Nov. 25, 1941.

H. W. STROBEL ELECTROSTATIC IGNITION SYSTEM Filed Dec. 31, 1940 13 NflcNsT/c FIE/.0 FL

- INVENTOR.

Patented Nov. 25, 1941 UNITED STATES PATENT OFFICE 2,263,958 nrac'raos'ra'ric rom'rron SYSTEM I Howard M. Strobel, Allegany, N. Y.

Application December 31; 1940, Serial No. 372,561

16 Claims.

cathode type to ignite or fire a high power dis-- charge tube of the cold cathode mercury pool type, and to provide means whereby the auxiliary tube is protected from being destroyed by the high currents passing through the high power discharge tube.

Discharge tubes of the mercury pool cathode type when used as rectifiers for alternating current can be fitted with systems for controlling the instant of starting the discharge at some predetermined interval after the anode potential becomes positive. To mention two conventional systems, one type keeps the cathode continuously active, by a sustaining discharge and utilizes a negatively charged grid interposed between cathode and anode to block the discharge to the,

positive anode until some selected instant when the negative grid charge is reduced, and another type uses a cold cathode mercury pool which is and so protecting the auxiliary tube from de-' fired or sparked by special apparatus at the instant in which it is desired to initiate the.

discharge.

The grid controlled tube provides easy electrostatic control but has the disadvantage of requiring a grid structure which will not' be damaged by the large currents existing during,

operation and of requiring a sustaining discharge to keep the cold cathode'active. The cold cathode ignition type of tube dispenses with a grid structure in the discharge tube but requires a large surge current of considerable power to.v

ignite" the tube.

It is the object of the invention to provide means for electro-statically controlling the instant of initiation of the mercury pool discharge tube while at'the same time dispensing with, the need of an elaborate grid structure in the main discharge chamber and also dispensing with the need of a sustaining are at the mercury pool cathode.

The present invention includes a main or conthe two tubes in such a manner as to permit-'- electrons originating in the auxiliary tube to be directed toward the mercury cathode and to pass into the main tube, said connecting region being adapted to the use of a magnetic field for deflecting the resulting discharge against the mercury surface, thereby transferring the cathode end of the main discharge to the mercury pool cathode,

struction by the large currents flowing through the main rectifier tube.

The transferrence of the cathode end of the discharge to the mercury surface depends upon the formation of a hot spot or cathode spot on the surface 01' the mercury. When this cathode spot is formed the main discharge takes place through the cathode and anode ofthe main tube. The cathode spot, which is characterized ,by electron emission, is created by electro-static and magnetic means. To this end the electric discharge is directed toward the mercury surface, and deflected toward and concentrated at the mercury surfaceby favorable structural design and the use of magnetic fields of either self-induced or external origin-' so that secondary emission is favored. Concentrating the discharge at the mercury surface forms a close lying positively charged layer that gives rise to a high intensity field which is favorable to the cold emission of electrons at the cathode spot. External circuit connections to the tubes can be such as to apply the line voltage between the mercury cathode and the discharge path itself.

More particularly, the invention consists in the system and method hereinafter described, illustra ed in the accompanying drawing and defined in the claims hereto appended, it being understood that various changes in form, arrangement and details both of circuits and of method within the scope of the claims may be resorted to without departing from the spirit or sacrificing any of the advantages of the invention. I

A clearer understanding of the operation of the invention and its improvement over known methods can be obtained by reference to the following figures and the descriptions relating thereto.

Figure 1 is a block diagram showing the arrangement of the principal elements in their operative relationships.

Figure 3 shows an enlarged view oi. a V-cut I Q cylinder made from magnetic material which is used in the connector-region of the device shown in Figure 2.

Figure 4 shows one type of restricting plate that may be used in theconnector-region of the device shown in Figure2.

Figure l is a block diagram showing the arrangement of the elements of the device in their operative relationship. The block l indicates a rectifier discharge tube having a cold cathode, as of the mercury pool type. Block H indicates a grid controlled discharge tube of the hot cathode type. Theblock I2 indicates the connectonregion joining the elements In and II, and within which region, as indicated by the dotted circle iii, a magnetic field is used to deflect the discharge current therein into the mercury surface.

The grid controlled discharge tube ll of the hot cathode type initiates a discharge therein. and is so adjoined to the main rectifier tube It as to also initiate a discharge of electrons to its anode. This discharge which "fires the main tube I0 must pass through the connector-region l2, where it is necessary that the cathode end of the discharge be rapidly transferred to the mercury pool cold cathode of III before the main discharge tube l0 should build up such a large current as would destroy the hot cathode of the firing tube II. The hot cathode may be further protected by the use of suitable limiting impedances in that branch of the circuit energized by the main rectifier voltage during the initiation period. The rapid transfer of the discharge is promoted by the structure of the connector-region, by magnetic fields either self-induced or externally supplied, and by such electro-static I means as will assist the transfer. The apparatus shown in Figure 2illustrates the application of these means.

Figure 2 shows the main rectifier tube ID, the firing tube II, and the connector-region 12, and in association therewith the various control circuits that may be used in connection with the operation and control of each of the above elements. The main rectifier I0 is energized by an alternating current supply at the terminals l520. The current fiowthrough the main tube Hi when its anode I1 is positive is from terminal l5 through load It, anode I! to mercury pool cathode .l8, through switch I! and back to terminal 20. The grid controlled firing tube H has the dotted circle l3, of such sense as to deflect any discharge therein against the mercury surface.

' The external magnetic field is supplied by the electro-magnet 26, which is energized by the coil 21 and switch l9 so that it can be placed in serice with the current passing through the main tube In, and which may also be energized by the coil 28, reversing switch 29, and switch 24, so that it can be placed in series with the current fiowing through the plate of the firing tube II. The self-induced magnetic field which surrounds the discharge itself can be used to deflect it toward the mercury surface by vuse of a V-shaped collar 40 of material-of magnetic permeability, which is shown more fully in the enlarged view of Figure 3.

Figure 3 is an enlarged pictorial view of the V-shaped collar 40. The cylinder 40 is made of -magnetically permeable material, such as iron,

having a V-shaped slot cut longitudinally in the topside. The collar 40 is so positioned in the connector-region l2 that the initiating discharge,

- current passes through the V-shaped slot. Since conventional anode 2|, grid 22 and hot cathode 23, and is energized, both as to its plate power former 30, which in turn may be connected across this discharge current is surrounded by a selfinduced magnetic field, part of the magnetic field will be through the magnetic material of the V-shaped collar 40. By principles well known to the art, an electric current discharge fiowing through a region of non-uniform magnetic permeability, will be deflected in such a direction as will permit it to set up the maximum number of magnetic lines of force around itself. The structure of the V-shaped collar is such that this optimum condition exists in the bottom of the V, and hence a discharge through the V-shaped collar 40 will be deflected, due to its self-induced magnetic field, down into the bottom of the V. It might be remarked that the above condition holds only when the magnetic field density through the collar 40 is not sufiiciently dense as to cause saturation, a condition which can easily be obtained by proper design. As will be seen by the drawing, a part of the bottom side of the V-shaped collar has been cut away so as to permit the mercury to enter the bottom of the V-slot when the piece 40 is used as shown in Figure 2. In Figure 3, the facing plates 4| and 42 which line the V-slot of 40 may be made of a material which is wetted by or amalgamates with mercury, such as brass, so as to favor the formation of a film of mercury on their surfaces. The mercury film is to assist the transfer of the cathode end of the discharge to the mercury.

the terminals [5-20. The transformer 30'energizes the plate supply transformer 32 and the grid control transformer 33 through the phase shifting circuit 3|. The phase shifter 3| determines the relative phase of the voltages applied to the elements of the firing tube II as referred to those applied to the main rectifier tube I 0, thus permitting flexibility of control. Transformer 32 applies a voltage to-the tube H through the circuit hot cathode 23, transformer secondary 32, switch 24 to anode 2|. plies the grid control voltages through the circuit hot cathode 23, phase shifter 25, transformer secondary 33 to grid 22. The connector-region l2 joins the firing tube H with the main rectifier tube l0, and it is within this region that the dismercury pool cathode 18. A magnetic field is applied through the region indicated by the Figure 4 shows a disc 45 which has a V-shaped cut in it. The disc 45 may be made of ma- ,terial which is wetted by or amalgamates with mercury, so as to favor the formation of a film of mercury on itssurfaces. The disc 45 may be used in the connector-region 12 of Figure 2, in place of 40. If disc 45 is used, the deflect- 'ing magnetic field would be supplied externally.

As shown in Figure 4, the disc 45 is designed so as to permit the surface of the mercury 46 to extend through the bottom of the V-shaped slot. In itsoperation, once the initiating discharge takes place through the connector-region l2, the magnetic field builds up simultaneously and deflects the discharge downward into the narrow V-slot and against the mercury surface. The V-slot performs the function of increasing the current density of the discharge, and hence assisting the transfer of the cathode end of the discharge to the mercury pool cathode. It will be obvious that the v-slot opening heed not necessarily be vertical, since one side could be ing periods of current increasedifference attracts the positive ions in the discharge toward the surface of the mercury, and contributes towards building'up a high intensity fieid at the mercury surfacegwhich is one of the conditions necessary forthe' creation-of a cathode spot for electronic'emission from the formed by the mercury surface, and the desired concentration of the discharge be secured by Under these conditions it will also be noted that no magnetic field exists in the connectorregion I2, hence an electron can pass freely through it without deflection. The instant at I .which'the grid controlled firing tube u initiates j the discharge is controlled by the setting of p the phase shifters 3| and 25. When the firing or ignition instant occurs, a'sdischarge of electronstakes place from the hot cathode 23 past the blocking grid (whose negative-blocking potential has just been removed) 22 to anode 2|. This initiates a discharge current ofelectrons through the external circuit anode 2|, through switch 24, transformer 32' to hot cathode 23.

The anode 2I of the tube II is designed with an opening or openings to permit high velocity electrons that are drawn toward it from the hot cathode 23 to pass through it toward the connector-region I2 and to s the main chamber of the tube I0, where the positive potential on the anode I'I immediately attracts them and initiates a discharge between the hot cathode 23 and the anode I'I. Simultaneously withlinitiating the discharge to theanode I1, the immediate object of the invention is to transfer,

its cathode end to the mercury cathode I8, by

creating a cathode spot thereon, thereby pro- 'tecting the low capacity hot cathode 23 from injury or destruction.

During the existence of a discharge between hot cathode 23 andanode II, the electron current flow is from terminal 28, through switch I9, to limiting resistor or impedance 36, through switch 35 to the hot cathode 23, anode I1, to terminal I5. Since the potential of 'the discharge in the connectorregion I2 is at about the same potential as the hot cathode 23 (except for the cathode .voltage drop, which is small) the action of the dropping resistor 36 is to make the mercury cathode pool I8 in the connector-region I2 at a high negative potential with regards to the discharge through the connector-region I2. The impedance 38 may also contain inductance, which would serve to develop a high back voltage dur- This potential cold cathode I8. It follows that the value of the dropping resistor or impedance 38 can be set at Sikh a value as will protect the hot cathode 23 from damage when the main line volt-.

age across terminals I '2Il is energizing the circuit cathode 23 to anode I1. Deflection of the discharge into the mercury surface is obtained by magnetic reaction, the magnetic fields being obtained by self-induction or from external sources. The action of the V-shaped" collar 48 has already been explained in connection with Fi e 3. ,The externalmagnetic field is supplied by the electro-magnet 26; which may be energized by either or both of the coils 21 and 28. If the switch I9 is open, the electron dis charge current flowing from 28 through coil 21 to the hot cathode 23 will also create the desired magnetic field across the connector-region I2. When switch 24 is open, coil 28 is energized by the current in the plate circuit of the firing tube II. A reversing switch 28 in the coil 28 circuit may be included to permits choice of its polarity, so that if desired the field across the connector-region I2 will aid in deflecting the first primary initiating electrons from the hot cathode 23 in an upward curve toward the anode I'I. Under. the latter condition, the magnetic field supplied by coil 21 would have to be the stronger one, so that once the discharge was initiated it could then be deflected downward against the mercury sur-. face.

Once the cathode end of the discharge has been transferred to the cold cathode I8, in the connector-region I2, the action of the magnetic field, which is sustained by the current flow through the main tube, will be to deflect the cathode spot out of the connector-region I2 and into the central portion of the cathode mercury pool I8. After the transfer of the cathode endof the discharge to the mercury surface, it will be evident that the continued existence of the magnetic field through the connector-region I2 will prevent the cathode I8 from supplying electrons to the hot cathode 23 of tube II, when, on the voltage reversal which may occur in the plate circuit of tube ll before it does in the main tube III, the cathode I8 and anode 2|, being joined through switch 34,

will be at a negative, potential with respect to the hot cathode 23.- The existence of such a condition would prevent the grid 22 from-regaining control, and hence would impair the operation of the device. Under the condition that the switch 34 is left open, and the anode 2I and cathode I8 are separate, the proper voltages do not exist to encourage reverse electron flow through the firing or ignition tube II. i

It will be observed that in the matter of aiding the rapid transfer of the cathode end of the discharge to the cathode I8, that when the grid 22 releases the electron flow-from cathode 23 to plate 2I, that many of the accelerated electrons continue on through to strike the surface of the mercury in the connector-region I2. The velocity'of these initial electrons will depend upon the voltage applied between cathode 23 and anode By including a limiting resistor 31 in the protecting the hot cathods 23 from an excessive current ,flow. The resulting high velocity electrons, 'by reason of their increased energies,-will be better able to cause secondary emission 'of electrons'at the point on the mercury cathode l8 where they strike. I

Underthe condition that switch 34 is closed, it will be noted that cathode I8 and anode 2I are at the same potential when no current is flowing through resistor 38, so the anode 2I could be omitted from the structure of tube II. Inthis case, the original initiating discharge would take placefrom cathode 23 through grid 22 direct to the mercury anode" I8.

It will be noted that the structural design and arrangement of the various related components .of the invention are such as to enable tube II to initiate a discharge in tube I0 through the connector-region I2, but that the discharge due to the cathode hot spotin tube I8 is prevented cathode 23 negative with respect to positive anode I claim: l

1. In a system comprising a main discharge tube having a cold cathode, a grid controlled auxiliary discharge tube having an active cathode, and a connector-region having a restricted opening which joins said main and said auxiliary tube chambersand contains therein an extension from the cold cathode of the main tube, said main and auxiliary cathodes being joinedthrough an impedance, the method of activating the cold cathode of said main tube which includes the steps of energizing the system, initiating an auxiliary discharge in said auxiliary tube, directing a portion of said auxiliary discharge toward said connector-region and into said main tube chamber, thereby initiating a discharge to the anode of said main tube, and laterally deflecting and concentrating said portion of said discharge in said connector-region against the surface extension therein oi the cold cathode of said main tube, whereby the cathode end of the main discharge is transferred to the cold cathode said main tube.

2. In a'system comprising a main discharge tube having a cold cathode, a grid controlled auxiliary discharge tube having an active cathode, and a connector-region having a restricted opening which joins said main and said auxiliary tube chambers and contains therein an extension from ,the cold cathode of the main tube, said main and auxiliary cathodes being Joined through an impedance, the method of activating the cold cathode of said main tube which includes the steps of energizing the system, initiating an auxiliary discharge in said auxiliary tube, directing a portion of said auxiliary discharge toward said connector-region and into said main tube chamber, thereby initiating a discharge from the active cathode of said auxiliary tube to the anode of said main tube, and magnetically deflecting and concentrating said portion of said discharge in said connector-region into the surface extension therein of the cold cathode of said main tube, whereby the cathode end of the main discharge is transferred to the cold cathode of the said main tube.

3. In a system comprising a main discharge tube having a cold cathode, a grid controlled auxiliary discharge tube having an active cathode, and a connector-region which joins said main and said auxiliary tube chambers and contains therein an extension from the cold cathode of the main tube, said main and auxiliary cathodes being joined through an impedance, the method of activating the cold cathode of the said main tube which includes the steps of energizing the system, initiating an auxiliary discharge in said auxiliary tube, directing a portion of said auxiliarydischarge toward said connector-region and into said main tube chamber, thereby initiating a discharge to the anode of said main tube, and magnetically concentrating by lateral deflection said portion of said discharge in said connector r the region against the surface extension therein 01 the cold cathode of said main tube, whereby the cathode end of the main discharge is transferred to the cold cathode of the said main tube.

4. In a system comprising a main discharge tube having a mercury pool cold cathode, a grid controlled auxiliary discharge tube having an active cathode, and a connector-region which joins said main and said auxiliary tube chambers and contains therein an extension from the cold cathode of the main tube, in which said system said main and auxiliary cathodes are Joined through an impedance, the method of activating the cold cathode of said main tube which includes the steps-of energizing the system, initiating an auxiliary discharge in said auxiliary tube, directing a portion of said auxiliary discharge toward said connector-region and into said main tube chamber, thereby initiating a discharge to the anode of said main tube, and utilizing the current flow to the main discharge tube to create a transverse magnetic field through the connector-region and to deflect the discharge therein against the said mercury surface extension, whereby the,,cathode end charge is transferred to the cold cat "ode of the said main tube.

5. In a system comprising a main discharge tube having a mercury pool cold cathode, a grid controlled auxiliary discharge tube having an active cathode, and a connector-region which joins said main and said auxiliary tube chambers and contains therein an extension from the cold cathode of the main tube, said main and auxiliary cathodes being joined through an impedance, the method of activating the cold cathode of said main tube which includes the steps of energizing the system, initiating an auxiliary discharge in said auxiliary tube, directing a portion of said auxiliary discharge toward said connector-region and into said main tube chamber, thereby initiating a discharge to the anode of said main tube, and utilizing the current flow to the main discharge tube to create a deflecting transverse magnetic field through the connectorregion and to create a potential difference betweensaid discharge in the connector-region and the cold cathode extension therein, whereby the cathode end of the main discharge is transferred to the cold cathode of the said main tube.

. 6. In a system comprising a main discharge tube having a mercury pool cold cathode, a grid controlled auxiliary discharge tube having an active cathode, and a connector-region which joins said main and said. auxiliary tube chambers and contains therein an extension from the cold cathode of the main tube, said connector-region containing a region of non-uniform magnetic permeability having the direction to the point of least magnetic reluctance for the magnetic field set up by any discharge therein toward said mercury surface extension, the method of activating the. cold cathode ofsaid main tube which includes the.steps of energizing the system, 1111- tiating an auxiliary discharge in said auxiliary tube, directing a portion of said auxiliary discharge toward said connector-region and into said main tube chamber, thereby initiating a discharge to the anode of said main tube, and limiting the main current flow through the auxiliary cathode, whereby the said discharge to '7. In a system comprising a main discharge tube having a mercury pool cold cathode, a grid controlled auxiliary discharge tube having an active cathode, and a connector-region having a restrictedopening which joins said main and said auxiliary tube chambers and contains therein an extension from the cold cathode of the main tube, said extension serving also as the anode for the auxiliary tube, the method of activating the cold cathode of said main tube which includes the steps of energizing th system, initiating an auxiliary discharge in said auxiliary tube between its active cathode and the cold and a connector-region,* 'said. main tube having a cold cathode with anode andincluding an energizing source, .saidauxilia'ry tube having an active cathode with anode and grid and including energizing sources, said main and auxiliary cathodesbeing joinedthr'ough an impedance, and

said connector-region Joining said main and said auxiliary tubechambers and containing therein an extension from the cold cathode of the main tube, means for initiating-an auxiliary discharge in said auxiliary tube,,means for-directing aportion of said auxiliary discharge towardsaid concathode of the main tube, directing a portion of said auxiliary discharge into said main tube chamber, thereby initiating a discharge to the anode of said main tube, limiting the main current flow through the auxiliary cathode as induced by the said main energizing source, and utilizing the current flow to the main discharge tube to create a transverse magnetic field through the connector-region which is adapted to deflect .and said connector-region having a restricted opening joining said main and said auxiliary tube chambers and containing therein an extension from the cold cathode of the main tube,

means forinitiating an auxiliary discharge in.

said auxiliary tube, means for directing a portion of said auxiliary discharge. toward said connector-region and into said main tube chamber, thereby initiating a discharge to. the anode of said main tube,- and means for laterally deflecting and concentrating said portion of said discharge in said connector-region against the surface extension therein of the cold cathode of said main tube, whereby the cathode end of the main discharge is transferred to the cold cathode of the said main tube.

9. In an ignition controlled apparatus comprising mainand auxiliary vapor discharge tubes and a connector-region, said main tube having a cold cathode with anode and including an energizing source, said auxiliary tube having an active cathode with anode and grid and .including energizing sources, said main and auxiliary cathodes being joined through an impedance, and said connector-region joining said main and said auxiliary tube chambers and containing therein anextension from the cold cathode of the main tube, means for initiating an auxiliary discharge in said auxiliary tube, means for directing a portion of said auxiliary discharge toward said connector-region and into said main tube chamber, thereby initiating a discharge to the anode of said main tube, and means for magnetically deflecting and concentrating said'portion of said discharge in said connector-region against the surface extension therein 01' the cold cathode of said main tube, whereby the cathode end of the main discharge is transferred to the cold cathode of the said main tube.

10. In an ignition controlled apparatus comprising main and auxiliary vapor discharge tubes nector-region and into said main tube'chamber, thereby initiating a discharge to the anode of said main tube, and means for magnetically concentrating by lateral deflection said portion of said discharge in said connector-region against the surface extension therein of the cold cathode of said main tube, whereby the cathode end of the main discharge is transferred to the cold cathode of the said main tube.

11. In an ignition controlled apparatus comprising main and auxiliary vapor discharge tubes and a connector-region, said maintube having a mercury pool cold cathode with anode and including an energizing source, said auxiliary tube having an active cathode with anode and grid and including energizing sources, said main and auxiliary cathodes being joined through an impedance, and said connector-region joining said main and said auxiliary tube chambers and containing therein an extension from thecold cathode of the main tube, means 'forinitiating. an auxiliary discharge in said auxiliary tube, means for directing a portion of said auxiliary discharge toward said connector-region and into said main tube chamber, thereby initiating, a discharge to the anode of said main tube, and means for uti-- lizing the current flow to the main discharge tube to create a transverse magnetic field through the connector-region so adapted as to deflect the discharge therein against the said mercury surface extension, whereby the cathode end of the main discharge is transferred to the cold cathode of the said main tube.

' prising main and auxiliary vapor discharge tubes and a connector-region, said main tube having a -mercury pool cold cathode with anode and including-an energizing source, said auxiliary tube having an active cathode-with anode and grid an including energizing source -said main and auxiliary cathodes being joined through an impedance, and said connector-region joining said main and said auxiliary tube chambers and containing therein an extension from the. cold cathode of the main tube, means for initiating an auxiliary' discharge in said auxiliary tube, means for directing a portion of saidauxiliary discharge toward said connector-region and into said main tube chamber, therebyinitiating a discharge to the anode of said main tube, and means for utilizing th current flow to the main discharge tube to create a deflecting transverse magneticfield through the connector-region and to create a potential difierence'between said discharge in the connector-region and the cold cathode extension therein, whereby the cathode end of the main discharge is transferred to the cold cathode of the said main tube.

13. In an ignition controlled apparatus com-v prising main and auxiliary vapor discharge tubes having an active cathode with anode and grid and including energizing sources, said connectorregion joining said main and said auxiliary tube chambers and containing therein an extension from the cold cathode of the main tube and also containing therein a region of non-uniform magnetic permeability having the directionto the point of least magnetic reluctance for the magnetic fleld set up by any discharge therein toward said mercurysurface extension, means for initiating an auxiliary discharge in said auxiliary tube, means for directing a portion or said auxiliary discharge toward said connector-region and into said main tube chamber, thereby initiating a discharge to the anode of said main tube, and means for limiting the main current flow through the auxiliarypathode, whereby the said discharge to the main tube magnetically deflects itself into the mercury surface extension, thereby transferring the cathode end of the said discharge to the cold cathode of the said main tube.

14. 'In an ignition controlled apparatus comprising main and auxiliary vapor discharge tubes and a connector-region, said main tube having a mercury pool cold cathode with anode and including an energizing source, said auxiliary tube having an active cathode with anode and grid rent flow through the auxiliary cathode as induced by the said main energizing source, and means for utilizing the current ilow to the main discharge tube to create a transverse magnetic field through the connector-region to deflect the discharge therein against the said mercury surface extension, whereby the cathode end of the main discharge is transferred to the cold cathode of the said main tube.

15. In a system comprising a main discharge tube having a cold cathode, a grid controlled auxiliary discharge tube having an active cath' ode, and a connector-region which joins said main and said auxiliary tube chambers and contains therein an extension from the cold cathode of the main tube, said connector-region channel being restricted by a plate having an opening which converges towardthe mercury surface, said main and auxiliary cathodes being joined through an impedance, the method of activating the cold cathode of said main tube which includes the steps of energizing the system, initiating an auxiliary discharge in said auxiliary tube, directing a portion of said auxiliary discharge toward said connector-region and into said main tube chamber, thereby initiating a discharge to the anode of said main tube, and laterally deflecting and concentrating said portion of said discharge in said connector-region against the surface extension therein of the cold cathode of said main tube, whereby the cathode end of the main discharge transferred to the cold cathode of the said main tube.

16. In an ignition controlled apparatus comprising main and auxiliary vapor discharge tubes and a connector-region, said main tube having a cold cathode with anode and including an energizing source, said auxiliary tube having an. ac-

tive cathode with anode and grid and including energizing sources, said main and auxiliary cathodes being joined through an impedance, andsaid connector-region joining said main and said auxiliary tube chambers and containing therein an extension from the cold cathode of the main tube, said connector-region channel being restricted by a plate having an opening which converges toward the mercury surface, means for initiating an auxiliary discharge in said auxiliary tube, means for directing a portion of said auxiliary discharge toward said connector-region and into said main tube chamber, thereby initiating a discharge to the anode of said main tube, and

meansfor magnetically concentrating by lateraldeflection said portion of said discharge in said connector-region against the surface extension therein of the cold cathode of said main tube, whereby the cathode end of the main discharge is transferred to the cold cathode of the said main tube.

HOWARD M. STROBEL. 

